Black Spot Found in Grove Near Frostproof

Friday

Nov 30, 2012 at 3:06 PM

WINTER HAVEN | As they did with citrus greening five years ago, many Polk County growers probably figured they had a few years before they had to worry about citrus black spot, a fungal disease that surfaced in 2010 in Hendry and Collier counties.

By KEVIN BOUFFARDTHE LEDGER

WINTER HAVEN | As they did with citrus greening five years ago, many Polk County growers probably figured they had a few years before they had to worry about citrus black spot, a fungal disease that surfaced in 2010 in Hendry and Collier counties.

Wrong again.

Polk's first black spot case surfaced last month on a single orange in a grove owned by Ben Hill Griffin Inc. about a half mile north of the Highlands County line and three-quarters a mile east of U.S. 27, Greg Carlton said Friday.

Carlton is chief of the Winter Haven-based Bureau of Pest Eradication and Control at the Florida Department of Agriculture and Consumer Services.

State inspectors have surveyed 1,339 grove acres in a 9-square-mile area around the Griffin grove and found no other black spot-infected fruit, he said.

But that's not necessarily cause for relief.

Inspectors will have to return to the area in late January to see if the fungal disease has spread to any late-season Valencia oranges, which are harvested from March to June, Carlton said. That's because the signature black spots don't begin appearing on citrus fruit until it "breaks color" or changes from green fruit to its mature color.

The black spot infection surfaced on a Hamlin orange, an early variety harvested from October to March, he said.

"We've gotten conditioned to this stuff coming out of South Florida and ending up here," said Vic Story Jr., a Lake Wales-based grower and former president of Lakeland-based Florida Citrus Mutual, the state's largest growers group, referring to greening and citrus canker, bacterial diseases.

Story agreed the unexpected black spot find will serve as a wake-up call to Central Florida growers, which happened when it took greening only two years to travel up the state to Polk.

"I think growers here will take it (black spot) very seriously," he said.

Ben Hill Griffin III could not be reached to comment at his Frostproof office.

As the name suggests, black spot leaves lesions on oranges, grapefruit and other citrus fruit, making it impossible to sell on the fresh market. It does not affect juice quality.

The biggest concern for growers is that the disease leads to premature fruit drop, reducing the quantity of fruit harvested and thus the grove's profitability.

Growers in Brazil, which has been fighting the disease much longer than Florida, report a 16 percent fruit drop even in groves that have taken all the scientifically recommended precautions to control black spot, said Megan Dewdney, a plant pathologist at the Citrus Research and Education Center in Lake Alfred who has been studying the disease.

In Brazilian groves that don't attempt to control the disease, premature drop rates up to 80 percent have been reported, she said.

Florida citrus growers will lose money from black spot not only because of lower harvests, but because the measures recommended by Dewdney and other scientists to control the disease's spread increase grove caretaking costs. Caretaking costs have already doubled during the past five years because of the costs of fighting greening.

Those recommended practices include three additional chemical sprays during the spring and summer, when the citrus fruit is most vulnerable, said Paul Meador, a LaBelle grower with a grove that had one of the first confirmed black spot cases in 2010.

Also recommended is composting leaves and other tree debris under the trees and spraying with urea, a nitrogen compound, to hasten decomposition, he said. Infected leaves carry spores that they eject into the air, spreading the disease.

Those practices add about $250 an acre to caretaking costs, Meador said.

That's bad news particularly this season because the current farm price for early oranges on the cash market is no higher than break even, Story said.

Meador, a leader in the Florida citrus community, also advocates a statewide requirement for covering all truck shipments with tarps on the journey from harvest in the grove to a juice processing plant or fresh fruit packinghouse.

Currently, Hendry and Collier groves covering 20,191 acres are required under a U.S. Department of Agriculture regulation to tarp their fruit shipments, Carlton said. Griffin has also agreed to tarp his shipments coming out of the 270-acre infected grove.

Because of the additional costs and labor, a statewide tarping rule has been a hotly debated topic since black spot arose.

"It's like waiting for cancer to pop up somewhere else," Meador said. "Do we continue to take passive action against this disease?"

Tarping limits the possibility infected leaves will blow off an open citrus truck into a nearby grove, thus spreading the disease.

Because of that possibility, state agriculture inspectors have been surveying the major routes taken by citrus trucks to the state's major juice plants and packinghouses, Carlton said. That includes U.S. highways 27, 17 and 70, Interstate 75 and state and county roads.

The Polk black spot case was discovered in early November during one of those routine "corridor" surveys for black spot, he said. State inspectors had been surveying within a half mile of those roads during the past two years but went out a little farther along U.S. 27 this time.

A USDA lab on Nov. 16 confirmed an earlier state lab finding of the black spot infection.

An infected leaf blown from a fruit truck en route from a Collier or Hendry grove to a Polk packinghouse or juice plant could be the reason black spot made the big jump from those southern counties, Carlton said.

Without genetic testing, however, there's no way to determine if the Polk black spot strain is even related to the southern strains.

"No one truly knows how it got there or howl long it's been there," Mike Sparks, Citrus Mutual's chief executive, told Southeast Florida AgNet in an online interview.

Polk leads the state's citrus-producing counties with 82,572 grove acres and 9.9 million trees in 2012, according to USDA data. It historically leads the state in citrus production, as it did in the 2011-12 season with 31.2 million boxes. It ranked No. 1 in orange, tangerine and tangelo production and third in grapefruit.

[ Kevin Bouffard can be reached at kevin.bouffard@theledger.com or at 863-401-6980. Read more on Florida citrus on his Facebook page, Florida Citrus Witness, http://bit.ly/baxWuU. ]